MEMS sensors having a capacitive mode of operation such as can be used in particular as an inertia sensor, pressure sensor or microphone usually have, as a moveable electrode, a membrane or a reed which can be moved by the physical quantity to be determined. A counter electrode or back electrode is arranged at a defined distance with respect thereto.
In known MEMS sensors, the back electrode together with a mechanically stable layer carrying it forms a construction that projects above the base chip in cap-type fashion. In this case, one known material for the construction of the mechanically stable layer is silicon nitride. In stoichiometric form, it can be produced in a stable process with constant properties. What is disadvantageous, however, is that stoichiometrically produced silicon nitride produces a tensile stress that acts on the three-dimensional construction of the MEMS sensor and leads to the deformation thereof and thus also to a change in the position of the back electrode. As a consequence thereof, the distance between the moveable electrode and the back electrode is altered and in particular reduced. This adversely affects the sensitivity of the sensor since the construction deformed in the Z direction no longer has a defined distance between back electrode and moveable electrode. This makes it impossible to exactly measure the physical quantity to be determined.